Treating process



Dec. 31, 1940. J. w. PAYNE TREATING PROCESS 5' Sheets-Sh 2 Filed Feb,28' 1940 l ffioh IN EN R D81. 31, 1940. J w, PAYNE TREATING PRDCESSFiled Feb. 28, 1940 5 Sheets-Sheet 3 Dec. 31, 1940. J w, PAYNE 2,227,416

TREATING PROCESS Filed Feb. 28, 1940; 5 Sheets-Sheet .4

all n I W Job? W EMA E INVENTOR %z2@ %%m ATTORN Dec. 31, 1940. I w,PAYNE 2,227,416

TREATING rnoczss Filed Feb. 28. 1940 S Sheets-Sheet 5 71 paw/v DEGREEff: 400 500 600 700 300 900 [,000 M00 1,200 L300 1,400

056E615 f. INVENTOR BY J'o/m/ w Him/E ATTORNEY why Patented Dec. 31,1940 TREATING PROCESS John W. Payne, Woodbury, N. J, assignmto So-Ineorpora corny-Vacuum Oil mm,

YorLN.Y-.aeorporationoINe'York Application February 28, 1940, Serial No.321,164

9 Claims. (CL 252-281) This invention relates to the t of finely dividedsolid materials in the p of gases or vapors and/or heat at closelycontrolled temperatures. The invention particularly relates to theregeneration of spent adsorbent type materials such as clays, activatedclays, synthetic alumina-silica compositions, bauxite and the like whichhave been used in tending to exhaust the utility of the adsorbent byclogging, coating or impregnating it with liquid or solid materials of acombustible nature, as, ior example, oily, tarry, or carbonaceousmaterials and which is regenerated for re-use by the application of heatto the spent adsorbent resulting in the driving oil? or burning oil ofinactive impurities. This application is a continuation-impart of myco-pending application 210,150, filed May 26, 193B. Suitable apparatusesfor carrying out my present invention such as those disclosed hereinform the subject matter oi my co-pending application Serial Numberorator, filed June 14, M339, which, in turn is a continuation-in-part ofmy application Serial Number 210,150.

in regeneration of petroleum filter clays, for instance, as carried outtoday, the clay suffers a loss in emciency with each burning or regeneration until finally it cannot he regenerated to a suficieutly highactivity to warrant further regeneration, at which time the clay isdiscarded to waste. Since clays which have had a differ-- ent numher oihurnings have dliferent efnciencies, they are usually kept separate andseparately classified. In general filter clays are only regeneratedshout live to eight times and practically never more than ten to fifteentimes heiore they are thrown away.

The problem of regenerating clays is complicated hy the sensitivity ofthe clays to high temperatures. While temperatures around 900' to llfih"h. are desired to burn ofi impurities from the clay, temperatures aroundlI-lllll F. may pertill manently injure the clay. Moreover, if thetemperature falls too low, ineilicient regeneration results. The problemof keeping the temperature oi the clay within safe limits is greatlyinin view of the fact most clays to be regenerated have more than enoughcarbonaceous material deposited thereon to furnish the heat required forregenerating, it is quite probable that present methods in generalpermit overheating; this appears to be true, moreover, from the fact itwould be extremely diflicult to control precisely the temperature 01'all the clay in present methods. 7

In the past various methods have been devised for carrying out theregeneration of spent filter clay. One of the first employed merely anopen hearth upon which the clay was spread and burned. Today there arethree principal types of burners in general use. In the first type theclay falls or cascades over badles set at about a 15 angle through aflue countercurrent to gases of combustion. In the second type the clayis regenerated in a rotary kiln slightly inclined from the horizontal.In the third type, which probably is the most commonly used, multiplehearth burners are employed. These multiple hearth furnaces or burnersare substantially the same as used in the roasting of ore and are ofeither the Nichols-Herreshofl or wedge type. In

these burners the clay is slowly rabbled across each hearth, droppingfrom one to another until the bottom hearth is reached. In all of thesecommonly used burners the temperature is controlled principally byadding steam or water, cutting the fires, regulating clay feed rate andregulating the concentration of oxygen passed into the burner andtherefore the rate of oxi- .dation.

The h'lns or burners which are now in common use are relativelyineilicient because of absence of proper temperature control forpreventing over-burning of clays, comparatively small throughput perunit volume of burner, and illemcient utilization of the heat developedin homing the oil or other carbonaceous matter left on the clay, thusrequiring considerable quantities of additional fuel to completecomhustion.

Other apparatuses and methods have heen proposed but have not displacedthe three abovedescrihed burners to any appreciable extent. This veryfact that other burners have not been taken up by the art is believedconclusive that each one suggested is subject to limitations whichprevent regenerations as elficient as, or at least any more eflicientthan, those already enjoyed by the art. While such a fact is not usuallyso conclusive, it is believed to be in the present case in view of thetremendous amounts of clay used and thrown away each year and theincreased amount that is necessary because of the successive loss inefilciency. Moreover, in view of the fact that clays and like materialsare not used in just one industry but in many, with a universal desireexisting for improvement, it is believed impossible that any methodwhich eflects any substantial improvement over those now employed couldgo unnoticed and undeveloped. This view may well be appreciated when itis realized that a single lube oil reall) finery in the petroleumindustry alone may regenerate over 75,000 tons of filter clay each year.

As a result of my research I have striven to devise a method which wouldbe commercially feasible for handling large quantities of clay and wouldpermit burning off of inactive impurities from the clay at optimumtemperatures while at the same time affording such constant uniform heatcontrol of all the clay under such closely controllable temperatureconditions that substantially none of the clay would be subjected to adeleterious temperature. It is believed the improved results I obtainwith my present method are largely due to the fact that this methodpermits burning of clay under substantially these conditions. Fbr thesame reasons, my present process may be used with advantage in processesin general wherein finely divided solids are treated at closelycontrolled elevated temperatures.

It is an object of my invention to provide a method for the elevatedheat treatment of a moving stream of finely divided solids which permitsuniform temperature control over each solid being treated throughout theperiod of its treatment.

Another object is to provide a method of conducting a treatment whereina moving stream of solid particles is directly contacted with gases orvapors which method afiords a uniform temperature control over eachsolid particle throughout its presence in the treatment and makes properprovision for passage of the gases or vapors through the solidparticles.

A more specific object of the invention is to provide a method forsubjecting a stream of porous adsorptive material of relatively smallparticle size, or other small particle size solids, to a heat treatmentwherein the adsorptive material fiows countercurrent to gaseous mediumin substantially a solid column of particles with proper gas pathsformed therethrough and a uniform temperature control is maintained overeach particle throughout its period of treatment.

Still another specific object of the invention is to provide a practicalmethod for regenerating a moving stream of spent adsorptive materialsuch as filter clays and the like having carbonaceous impuritiesdeposited thereon by reacting said carbonaceous impurities with agaseous oxidizing medium which method suitably flows the adsorptivematerial countercurrent to the gaseous medium and controls thetemperature of the adsorptive material such that eflicient regenerationwill be eifected without subjecting the material to deleterioustemperatures.

An important object is the continued regeneration of filter clays to ahigher efiiciency than heretofore obtained which substantiallyeliminates progressive degradation in efficiency with successiveregenerations.

Another object is the provision of a method capable of accomplishinghigh unit throughput per unit of capital invested and space occupied.

An important object is the provision of a method capable of beingcarried out in an apparatus having few moving parts and capable of easyand economical maintenance and operation.

A further object is the provision of a method which permits moreeflicient utilization of the heat developed in the apparatus. These andother objects will appear from the following description of myinvention.

In my present invention, treatments comprising the contacting of solidparticles and gaseous agents at elevated temperatures are conducted byflowing the particles through a treating zone wherein every solidparticle throughout its entire presence in the treating zone ismaintained within sufiiciently close proximity to, but out of contactwith, a sufficient amount of properly temperature-controlled,circulating fiuid heat exchange medium that the temperature of each andevery solid particle while in the treating zone is kept within a propertreating temperature range without any deleterious temperatureoccurring. Furthermore all of the solids are flowed substantially thesame distance through the treating zone so that the treatment will besubstantially uniform, and, in order to properly contact the solids andthe gaseous agent in the treating zone, suitable provision is made forpassage of the gaseous agent through the zone without causingchanneling, whereby gaseous agent flows in a stream by itself withoutsufficient contact with the solids, and so that the gaseous agent mayfiow through the solids without unduly disturbing their generaldirection of flow.

Thus the present invention may be used in the treatment of finelydivided solids in general in order to change their physical or chemicalcharacter or both. Particularly typical of materials that may be treatedby my invention are those spent filter clays or other adsorbents derivedfrom the filtration of mineral oil products such as waxes, turbine andtransformer oils and particu l-arly the usual lubricating oils; or fromfiltration of vegetable oils; sugar liquors; etc., which spent clays orother adsorbents contain adsorbed combustible materials such as tarry,oily or carbonaceous matters and are regenerated for reuse by theheating or burning of the combustible material adsorbed thereon. In someinstances it may be desirable to burn ofi only inactive carbonaceousimpurities while car-bonizing a part of the carbonaceous impurities toform an active carbon layer on the adsorbent.

Other typical materials which may be treated are catalytic materialscomposed of solid particles which have been used in some catalyticprocess of refining or conversion until sufiiciently contaminated withimpurities that regeneration or revivification is required or desirableand wherein the inactive impurities deposited on the catalyst areremoved by treating the catalytic material at elevated temperatures. Forinstance, in the catalytic cracking of petroleum oils using a finelydivided solid catalyst material, e. g., claytype catalysts, the catalystbecomes contaminated with a carbonaceous deposit of the nature of cokewhich must be removed from time to time in order to regenerate thecatalyst, and this removal is usually eifected by burning off theimpurities at closely controlled elevated temperatures. Such catalysttreatments involve special problems and form the subject matter of theco-pending application S. N. 321,184 filed February 28, 1940.

For convenience the present process will be described in detail withrespect to regeneration of filter clay. However, it is to be understoodthe invention is not limited thereto but is directed to the whole fieldof regeneration of spent adsorbents by burning oiI inactive impuritiesas well as to the initial preparation of same, when necessary, includingactivating, drying, hardening and the like by the application of heat.Likewise the present process, as has been stated, may be used toadvantage for the heat treatment of solid particles in general, as, forinstance, in roasting of ores, certain drying processes etc.,

showing decided advantages for treatments wherein close temperaturecontrol is a necessity or a highly desirable condition and reactions areinvolved which produce or consume a considerable amount of heat.

In order that the invention may be readily out my invention which omitsthe heat exchanger zones shown in Fig. 1;

Fig. 6 is a cross-section on the line 6-8 of Fig. 5;

Fig. 7 is a perspective view of a preferred header structure for theheat transfer tubes of the alternate form shown in Fig. 5.

Fig. 8 is a cross-section taken on the line -4 of Fig.

Fig. 9 is a cross-section taken on the line 9-9 of Fig. 5;

Fig. 10 is a perspective view of a portion of another alternate form ofan apparatus suitable for carrying out my invention showing an optionalform of baflle structure, the view being taken at an angle somewhatbelow the horizontal looking up underneath the bullies;

Fig. 11 is a horizontal cross-sectional view of an apparatus containinginternal structure of the type shown in Fig. 10.

Fig. lit is a graph showing temperature control with variation ofcombustible materials on the solids; and,

Fig. 13 is a graph showing temperature control over a prolongedoperation using substantially the same feed.

Referring to Fig. 1, 10 indicates a burner or kiln in which there ishoused a burning zone il, a preheating zone i2, and an after-cooler i3.Spent adsorbent or other solids to be treated, stored in hopper I4 isfed to the upper end of the regeneration apparatus through a throat l5,and thereafter the adsorbent passes downward through zones I2, II, andI3, and is removed from the apparatus in revivifled or treated conditionby some device it, which may preferably be a star wheel mechanism orsome similar device for enabling the removal of adsorbent irrespectiveof the pressure maintained within the casing Hi. Air, or other suitablegaseous agent, under pressure is fed through inlet I1 and passes upwardthrough the casing it in countercurrent relationship to the descendingadsorbent, passing successively through zones l3, II, and I2. The airdeparts from the apparatus through outlet it and is led into separatorl9, which is a dust separator, preferably of the usual well-knowncyclone type wherein lines and dust, ii. any, are separated from themoving steam of air. These separated materials are removed from orreturned to the system through pipe 2| and air or flue gas is finallydischarged through pipe 2|. it is'obvious that these arrangements permitthe operation within the case to be carried out at pressures below,near, or materially in excess at atmospheric pressure.

Within the case ll, the functions carried out within the three zones areas follows: In zone I! incoming air is preheated by contact with burnedadsorbent, the adsorbent at the same time being cooled. In zone ii acombustion occurs in which the carbonaceous impurities are burned fromthe adsorbent. In zone I! another heat exchange occurs in which the hotflue gases are cooled and preheat the incoming adsorbent. The rate andpath of flow of air and adsorbent is so adjusted with respect to eachother that the supporting eifect of the rising column of air does notinterfere with the uniform downward flow of the column of adsorbent.Optimum conditions are reached when the velocity of air is quite highand in most cases it appears to be preferable that the velocity oi. theair is just short of that which will prevent uniform progress of theadsorbent through the apparatus. In the event a combustible materialsuch as bone char is being regenerated, an inert gas, if any, willwholly or largely replace air and regeneration eifected by heat alone,the inert gas sweeping ou the vaporized impurities being preferablyintroduced into the apparatus in the manner disclosed for vthe'air. Incase other gases are used in place of or in addition to air, they may beintroduced through air inlet i! or separate inlets may he provided.

In the regeneration of spent petroleum filter clays, for instance, asstated above, it may not always be desired to burn off all the petroleumcarbonaceous impurities but rather only inactive impurities. This may bedone by reducing the amount of air or concentration of oxygen to asuilicient extent to only burn all a part of the petroleum impurities.the remainder being carhonized to form an active carbon layer on theclay. The concentration of oxygen may be reduced by merely reducing theamount of air or by replacing a part or all of it with steam or inertgases. For some oils, notably solvent refined petroleum oils, yieldsfrom such carbonizm clays are from two to four times as great as fromthe same clay regenerated by complete burning.

The use of carbonized clays for filtering solvent refined oils iorms thesubject matter of a copending case Serial Number 275,673 filed May 25,1939, and the carbonizing of petroleum filter clays by procemes ingeneral rather than only the particular one herein disclosed terms thesub Ject matter of the co-pending application Serial Number 275,672,filed May 25, i939.

When combustion occurs under the circumstances above outlined in thepresence of spent absorbent containing carbonaceous impurities and airunder pressure and in the absence of other agencies, there is a decidedtendency to burning in a concentrated zone at extremely hightemperatures, ruinous to most adsorbents. Likewise in operations ingeneral of this type wherein there is a considerable consumption,evolution or application of heat there is a tendency for localized oreven general overor under-heating. In order to control this tendency andsuppress it, the burning zone is equipped with heat transfer tubes 22,through which there is circulated a fluid heat transfer medium whichenters by pipe 23, leaves by pipe 2!, and is circulated under theimpulses produced by pump 25. Headers 32 connect pipes 23 and 2! of theexternal circuit with tubes 22 and are of any suitable constructionwhich permits the clay to gravitate on through the space between thetubes. In order that control of the temperature of this circulating heattransfer medium may be had, there is inserted in the external portion ofits circuit a heat exchange means 25 which, dependent upon therequirements of the process being carried out, may effeet either coolingor heating. This heat exchange means I is provided with a by-pass 21 tofacilitate control of the temperature of the circulating heat transfermedium. To permit addition or withdrawal of heat transfer medium forsuch purposes, for example, as making up losses or shutting down thesystem, there is provided a pipe connection 28. Tubes 22a in the heatexchanger zones I 2 and I3 serve merely as spacing tubes for bodies 29.

A most important feature of the invention and one upon which thesuccessful carrying out of the operation is largely dependent, is theprovision of a proper treating or burning zone. To properly carry outthe steps of the operation disclosed herein using countercurrent flow,the adsorbent must pass at a practical rate through the treating zone inone direction and the air in the other direction without either beingallowed to channel or flow in a stream by itself without suiiicientcontact with the other medium. Furthermore, since my process isparticularly directed to treatments of relatively small particles, suchas percolation clays, ores to be roasted, etc., which small particlespack together sufiiciently that practically no gas voids are leftbetween them, I have found that in order to successfully treat thesesmall particles by my present process I must provide for suitablepassage of the gas through the particles. In order to provide feasiblee, I baiiie the gas and particles to form continuous, substantiallyparticle-free passages for the gas which permits the gas therein todirectly contact particles along at least one edge of the passages, or Iat least redistribute the particles and gaseous agent at suificientlyfrequent intervals that there is no such extended portion of downilowingparticles up through which gaseous agent must fiow as to causedifllculties, such as "boiling" of the clay, in these portions.

Therefore I have found that the structure of the treating or burningzones for carrying out my invention have two principal requirements,nunely, suitable passage means for circulating fluid heat exchangemedium and suitable baille means for the solids and gaseous agent. Thepassage means should be so arranged as to keep temperature-controlled,circulating fluid heat exchange medium within suiliciently closeproximity to each and every solid particle in the zone throughout theirentire presence in the zone that proper temperature control of eachparticle may behad. The particular arrangement or provision of the fluidheat exchange medium throughout the zone is especially important andwill be discussed more in detail hereinafter. The home means should besuch as to (1) cause all the solids to have about the same length offlow through the zone, (2) redistribute the gaseous agent and solids soas to prevent channeling, (3) aidinheat transfer (4) provide adequatepassageway for the gaseous agent up through and in contact with solids,and (5) force the gaseous agent to take such a route through the zonethat high rates of gas flow may be used without having any unde irableeffect on the general direction the solids are moving. The functions ofthe baflle means set forth in (4) and (5) are increasingly important thefiner the particle size of the solids.

Several structural means may be devised whereby the above requirementsmay be provided. Accordingly it is to be clearly understood that thepresent process is not to be restricted to the particular structuralmeans shown and described for illustrative purposes for carrying out theprocess. Particularly convenient means and one relatively cheap is thatinternal arrangement which is shown in Figs. 2-6, 8 and 9. In thisarrangement, there are shown the vertical heat exchange medium carryingtubes 22, and between those tubes there are shown various short piecesof light angle iron designated 29. These pieces of angle iron are soarranged that their length is placed horizontally and their angle isopen downward. Placed in this manner between the heat exchanger tubes22, each layer of angle irons 29 being disposed transversely to those onthe layer below, each angle iron serves to receive the adsorbentdescending from above and to distribute that adsorbent laterally inplanes at an angle to those planes in which the adsorbent was movingwhen it first encountered the particular angle iron in question. Alsothe form and placement of these angle irons and the manner in which theysurround the heat exchange tubes 22 causes adsorbent in its downwardfiow to repeatedly pass through the annular space 30 (see Figure 3),which annular space 30 surrounds the heat transfer medium tube andbrings the adsorbent into even closer heat transfer relationship withthe heat transfer medium in said tube.

Ascending air is trapped beneath each piece of angle iron. To preventits flow being concentrated at the ends of the angle irons against thewalls of the chamber, each angle iron is pierced at several points alongits heel forming a series of orifices 3|, these orifices being solocated that those in one angle iron will be directly below the closedpart of the next above angle iron which crosses this part of thefirst-mentioned angle iron. In this manner each orifice distributes airinto the space beneath the angle iron above it, yet air cannot passdirectly upward through another orifice. In short. the arrangement issuch that these orifices when assembled are not in register. It will beseen that by this arrangement gas passes up through the chamber in atortuous, substantially particle-free path .but that the gas is indirect contact with the particles flowing along the bottom boundaries ofthe gas passages. The result of this arrangement is a very effectivedistribution and redistribution of both downfiowing absorbent andupfiowing air, coupled with an elfective bringing of the adsorbent intoheat transfer relationship with the heat transfer medium flowing withintubes 22. Furthermore as stated hereinabove the use of relatively highair velocities are desired for practical regeneration. One of the primefeatures of baiiles 29 is that they permit the use of rather high airvelocities without boiling or blowing the clay or other material out ofthe apparatus. While baflles might be arranged so that gas would have topass directly up through small portions of particles, the sheltering ofthe path and redistribution of the particles should be frequent enoughthat the gas passes through such portions with no substantial diillcultysuch as boiling of the clay.

In Fig. 5, I show part of a modified form which dlii'ers from theapparatus of Fig. 1 in omitting the two heat exchanger zones at eachend. Since the heat exchanger zones are not absolutely essential forsuccessful operation and since careless operation might permit burningin these zones -which are not provided with fluid heat exchange medium,it maybe found more practical at times to use this form of my apparatus,which omits the heat exchanger zones. In Fig. 5, I also show channelmembers I! which are placed transversely across the top row of angleirons, covering in row form the orifices 3| opening to the top of thechamber and thereby collecting the rising air (see Figs. 8 and 9).Channel members 33 are provided with orifices 34 to which are attachedpipes 35 which lead upwardly to a point above the clay inlet opening ofthe throat It of hopper ll. This latter arrangement prevents the risingair from blowing the newly entering clay, which is above the angleirons, out

'ofthechamber. Afurtherfeatureofairpipes 3i isshowninl'lgs.5and9,namely,thecurved upper ends 3. Thus the pper ends of all oftheairpipes ll arebentmltwardlyinsuchfashionastoforcetheemergingairtonowinarotary manner thereby forminga centrifugal separator within the chamber, and, as a consequence ofwhich the finely divided particles or dust carried by the air areseparated out and drop back down while the particle-free air :w-a on upand out flue It. It is to be understood, of course, that if desired theair pipes I might lead up to the flue or outlet and an externalseparator used as shown in Fig. 1.

In Fig. I, I show in detail a preferred header structure which isparticularly suitable for an apparatus such as shown in Fig. 5. As shownseparate pipes 31, serve as manifolds to connect up rows of heatexchange tubes 22. Manifolds 3T areallinturnconnectedtoasinglemastermanifold pipe 38 through curved pipes 3!. The master manifold pipe 38connects with pipe 24 (see Fig. 1) of the external heat transfer mediumcircuit. A similar header at the bottom of the chamber connects withpipe 23 of the external circuit.

As stated above, several structural means may be devised for effectingthe desired baflling when treating a flowing stream of small particleswith a countercurrently flowing stream of gas. In Fig. 10 I show anotherbaliie structure comprising winding fins which may be used in place ofthe angle iron bafiles shown in the other cases. In fact, the finbaiiies of Fig. 10 have certain advantages over the angle iron in thatbeing welded to the tubes they give greater heat exchange surface to thetubes themselves, and, moreover, this fin structure has certainadvantages from the construction standpoint.

(ill

In Fig. 10, tubes 22 are provided in a manner similar to that shown inthe other cases which rovide tubes. but instead of placing angle ironsbetween the tubes, 9. metal fin II is welded to each tube, the tin beingwound continuously along the tube as shown. It will be seen in Fig. 11that be short-circuiting" of the clay in this area, andtheclayinthecentcrofthisareamight not be kept sumeiently close to heat exchangesurfaces. Of course, there might be a slight amount of this verticallyfree area before appreciably in- 5 ferior results are encountered.

Theobjectofhavingtheflnswindalongeachtubeistoprovidewindingsubstantiallypar-' tlcle-free gas ways up throughthe case underneath each which permit gas thereintodirectlycontacttheparticles alongatleast oneedgeoftheways.Whiletheflnsare shown as uniform helical baiiies they may be of anyequivalent structure which aflords the desired result.

In the preferred operation the particles flll the case, movingtherethrough in substantially a solid solumn of particles, and therebyform an outer side wall to the gas ways where the gas and catalyst arein direct contact. A further feature may be provided by using bailies ofmesh wireconstructiomthemeshofwhichistoofine to permit w w: e ofparlicles, and, thereby, the bumingorreactingsurfaceofthechamberispractically doubled since the burning or treating not only occurs alongthe above mentioned .outer side wall but also along the face of thebafiles that the particles move over.

While the fins might be positioned at right angles to the tubes or evenslanted slightly upward, most eflicient resultsarehadbyslantingtheflnsdownwardly to give them a slope which is at least asgreat as the angleofrepose of thepartlcles being used. 011 the other hand the slope 35should not be too great, as the sizeof the gas w: e is thereby reduced.I have found a slope of about 45 to be quite satisfactory for most uses.The pitch of the continuous spiral or helical fin should not be so greatthat the particles more or 40 less fall straight through the case, butrather should be at a more moderate pitch so that the particlessubstantially ride the baffles. Also if the pitch is too great no airpassage is provided. It may be found of advan age to have adjacent flnsof opposite winding so that particles riding down thereon will betraveling in opposite directions. collide and thereby effect morethorough redistributing.

The size of the particles that may be treated in my process is limitedby the air velocity required for feasible operation. For this reasonclay particles treated should be of a granular nature for best results,for intsance, 100 mesh or larger, as otherwise trouble may beencountered in obtaining a uniform downward flow of the solids. Theinvention is particularly feasible forregenerating filter clays ofaroimd 30-60 mesh. However it is to be und the invention is notrestricted as to the exact size of the particles but rather to thegeneral application of the process herein disclosed to solid particlesof any size wherein the objects of the invention are attained,particularly since particles of diflerent materials, e. a particles ofores to be roasted and spent porous particles to be regenerated, mayvary appreciably in weight for the same size. Since the heat transfer inthe present process should be partially by conductance, the treatingzone, for best results, should be filled with the solid particles whichthen gravitate m in a more or less solid column through the apps.-ratus.

An important feature of the present invention is the proper use of fluidheat exchange medium and the structure whereby the solids are intimatelycontacted with counter flowing gases while each individual particle ofthe solids, during substantially the entire. duration of the reaction iswithin sufficiently close proximity to the heat exchange medium that nodeleterious temperature condition is created.

In order to obtain proper temperature control, the heat exchange mediummust be adjusted to a proper temperature, for extracting or adding thenecessary heat. Moreover heat exchange medium must be flowed insufficient amount in close indirect heat exchange with every solidparticle and then cooled or heated to readjust its temperature by meansextraneous of the reaction heat before the mediums temperature reachesan undesired value. In this way the heat exchange medium in my inventioncontinuously controls the temperature of the zone making immediatebompensations for temperature changes whereby no deleterioustemperatures occur.

When, the operation is first started the heat exchange medium may addsome heat to help iniducted, below temperatures which cause h at damagethereto), and, of course, at a temperature above which undue coolingoccurs so that the regeneration .(or other treatment) can not proceedeiliciently. For instance. in the usual regeneration of fllter clays andthe like we preferably maintain the heat exchange medium at atemperature around 850-900 F. and never above about 1050 F. By socontrolling the heat exchange medium and flowing a suflicient amountwithin sufliciently close indirect heat exchange with each particle, aclose uniform temperature control is maintained over every particle sothat no deleterious temperatures occur which cause injury to theparticles or treating operation. Moreover the entire zone will bemaintained under the same close uniform conditions.

While temperature-controlled, circulating gaseous heat exchange mediumsof high specific heat might be used in some instances, I greatly preferthe use of liquid heat exchange mediums since necessary pumping andpressure facilities for proper use of even the best gaseous mediums, e.g.,

hydrogen, would, in many instances, render the operation commerciallyimpractical.

The liquid heat exchange medium to be used is preferably one which atthe temperatures encountered is possessed of a low vapor pressure, ahigh specific heat, a suitable viscosity and is not corrosive to theusual metals and other materials which may be used in construction ofthe apparatus. Many normally solid materials in their fused state formexcellent heat exchange mediums such as fused salts and fused metals andalloys. In the regeneration of clay, I prefer the use of fused salts. Aparticularly preferable mixture of this kind is a mixture of the alkalimetal salts of nitric and nitrous acids. In certain cases suitableliquid heat exchange media might be found which have a boiling pointaround the desired operating temperature, in which case, the heatexchange medium, although mostly in the liquid state, might undergo sometransition whereby advantage could be taken of its heat of vaporizationor condensation. By the use of liquid heat exchange media and by havingthem in sufliciently close proximity to all particles undergoingreaction an extremely close and uniform temperature control may bemaintained.

In the preferred practice the heat exchange 'medium is maintained atsubstantially the temperature of the treatment being controlled, e. g.,above the minimum temperature at which proper treating is obtained andbelow the minimum temperature at which undesirable heat injuries occursuch as substantial damage to the particles or reaction. Such practicemay be carried'out effectively when the heat exchange medium is a liquidand has a relatively high specific heat and the structure of theapparatus is such that heat exchange medium is brought within closeproximity to every granule in the apparatus. Hence considerablefluctuations in temperature in either direction can be compensated bythe liquid heat exchange medium without substantially altering itstemperature and suitable cooling or heating of the heat exchange mediumand its circuit maintains the liquid at the treating temperature.

. Thus if a sharp brief rise in temperature occurs which normally woulddamage the clay before it is indicated, if ever, on a temperatureresponsive device and suitable manipulation effected to offset the rise,in the present method the liquid heat exchange medium would immediatelyand automatically offset the rise by absorbing any excess heat so thatdeleterious temperatures would not be created. Likewise if thetemperature fell 01! sharply so that normally the temperature would goso low that ineflicient regeneration would result, this fluctuationlikewise would be immediately and automatically offset by the liquidheat exchange medium which would add heat to the cooling granules. Afurther advantage in this practice results from the complicatedstructure of apparatuses for affording proper temperature control. Thestructure involves an exposure of tremendous amounts of heat conductingwalls. When two widely different temperatures are maintained ondiiferent sides of these walls thermal expansion difficulties may arisecausing buckling, etc. However when substantially the same temperatureis maintained throughout, the apparatus operates without strain ordifliculty.

As a result of the close uniform temperature control afforded by myprocess many important advantages are obtained. For instance, theprocess of regenerating spent filter clays by buming is substantiallyrevolutionized. Thus in my process, since I provide adequate temperaturecontrol, I preferably use not substantially more than the theoreticalamount of air or oxygen to burn the carbon as contrasted to priormethods which use large excesses of oxygen. As a consequence the carbonon the clay or adsorbent usually furnishes all the necessary fuel" forburning so that no additional fuel need be added,

.It is to be noted however that these exchange mediums add heat ratherthan extract, and, moreover, being at high temperatures, aboveclay-damaging temperatures, they subject the clay to additional dangers.

In some treatments, as for instance, in carbonizing some clays, thereaction or treatment may not give out suflicient heat for its needs orit may even be endothermic. In such a case my heat exchange medium willsupply heat to the operation rather than extract heat, nevertheless, theprinciples are the same with the medium being heated by the extraneousmeans rather than cooled and as before always maintained belowtemperatures which cause heat damage to j the clay or other material ortreatment being conducted.

As has been indicated hereinabove, one of the important features of thepresent invention is the provision of a treating zone whereby thecirculating fluid heat transfer medium may be maintained at all timeswithin sumciently close proximity to every granule in the burning zonethat no deleterious temperatures will be created. Obviously this maximum'distance that each granule might be from the heat transfer medium mayvary with the materials treated, the atmosphere in the burning zone, thereaction being carried out, the amount of impurities being burned, massvelocity of air, physical properties till to which my apparatus may beput. However, in

general, this distance should not exceed about 1 /2 to 2 inches in orderto afford proper temperature control, a distance of 1% inches being wellsuited to the regeneration of clay. Furthermore, it has been found thatthe volume expressed in cu. in., that may be occupied by the clay orother material should be about if; to 3 times the area of heat transfersurface, expressed in sq in., (exelusive of the angle irons or otherbailies). In the regeneration of fullers earth it is preferred tomaintain this ratio within the range of about /5 to it.

With the above guides, the concept that the clay or other material is tobe passed through a zone of substantial length to afford proper contacttime with each particle in sufliclently close proximity to the heatexchange medium that no deleterious temperature will be created at anypoint and the further concept that the burner is to be providedthroughout with baflie means which provide passages for the air, preventchanneling or short circuiting of the clay and air thereby permittingfeasible air velocities to be used which do not stop the uniform counterflow of the clay, it is believed any worker in the art will have littletrouble in designing the particular apparatus for his uses whichincorporates the present invention and thereby permit him to carry outthe present invention.

The rate of heat liberation per unit of time per unit of volume is afunction of the mass velocity oi adsorbent, of the amount of carbon tobe burned therefrom, and of the mass veiocity of the air.Experimentation has established that optimum conditions of burning occurin those ranges of mass velocities wherein the adsorbent is almostsupported by the rising air, the upper limit being of course at airvelocities so great that adsorbent of the size being burned will notfall, but will float. Since this velocity will vary with the apparentspecific gravity of the clay, which apparent specific gravity is afunction of the real specific gravity and the particle size, thelimiting velocity is not a single velocity, but a range, defined asabove. The inter-relation of adsorbent rate, carbon, and air rate may beexpressed best as that combination of rates, which in the case oifullers earth, for example, while not'exceeding about 1150' F. underconditions of operation, will remove carbon at the rate of about 0.3 toabout 2.0 pounds per hour per cubic foot of chamber volume for a broadrange of possible operation, and from about 0.5 to 1.5 pounds per hourper cubic foot of chamber volume for preferred operation. The massvelocity ofheat transfer medium of course depends upon the speciflc heatand other characteristics of the medium. In operations where it isdesirable to maintain the adsorbent at a relatively uniform temperature,the mass velocity is best defined as that mass velocity of heat exchangemedium which will extract the required amount of heat while undergoing atemperature riseof not greater than about 50 F. and preferably of from 2to 10;

That the present process is capable of close.-

temperature control is shown by the graphs presented in Figs. 12 and 13.Fig. 12 illustrates that the temperature can be maintained within verynarrow limits even when the nature of the clay feed is altereddrastically over short-time intervals, For the particular data of Fig.12 the oil content of the feed clay was varied from to at 30 minuteintervals with clay turnover in the kiln once each hour. 'Ihe'precisetemperature control of which the process is capable is furtherillustrated in Fig. 13 which gives actual operating-temperature-curvesfor various clay zones in my kiln for a period of several hours during afull-scale commercial operation. In this particular operation the clayrate was 21 lbs./hr./cu. ft. of kiln volume and there was 7.2% ofcarbonaceous material on the unburnedclay. The graph clearly shows thatthe temperatures in the various zones remained practically constant from5 p. m. to 1 a. m. in an actual commercial operation.

Hereinabove it has been usually indicated that the temperature ofburning should not rise above about 11501". This temperature is specificto materials of the nature of fullers earth, and for diiferent materialshaving different optimum regeneration temperatures, the proper specifictemperature should be the basis of design and operation.

To show specific application of the above broad considerations ofdesign, the following examples are given. Both are based uponregeneration of fuller's earth, 30-60 mesh, from percolation filtrationof lubricating oil, using a molten salt heat exchange medium, the clayhaving been washed, steamed and removed from the filter in the usualmanner, containing about 0.5% to 5.0% by weight of "carbon and up toabout 20% by weight of moisture. The dimensional relations are as shownbelow:

Kiln A Kiln B Length of chamber feet 13 feet. Length of burning zonc.-.8 feet 10 feet. Length of heat exchange mnes (pi-e 1 foot 1.5 feetheated and after-cooler). Size heat transfer tubes std. pipe ii" std.pipe. Spacing of tubes (triangular) 1%" centers 2%" centers. Size ofangle irons 9in x 946.. l x Diameter of holes in angles 0.46" 0.60.Volume of chamber occupied by day. 50% 51%. Hydraulic radius for heattransfer. 0.53" 0.83

Air clay contact surface (sq. inches] 1.89 1.09.

cubic inches clay). Maximum coke burning rate (#lhour/ 0.60 0.61'.

cubic foot of chamber). Maximum clay thruput to burn 3% of 23 l9 coke(#lhour/cu. ft. of chamber). Pressure drop of air'for above rate.---. 30water 19" water.

Multiple hearth My kiln kiln Thus it will be seen the multiple hearthfurnace has a diameter nearly 5 times greater and a weight timesgreater. Moreover the above 20 data shows that per unit volumerthecontacting temperatures 01 about 1000-1050 F. the temperature control iseasy and positive and no portion of the clay need rise above 200 F.higher than the temperature of the heat transfer medium.

The gain in filtration efllciency that may be derived from use of mymethod for regenerating filter clays is revolutionary in ammmt and itssuperiority over conventional methods is believed best shown by thetabular data set forth in the following Table I, wherein clays burned ona commercial scale by my present method are compared in percolationdecolorlzlng emciency of various typical oilswithclaysbumedinoneof thebest type of equipment at present available, the clay being used toexhaustion in percolation prior to each burn and being drained, washed,and strained as understood in the art. (Fresh burned clay was consideredas 100% eflicient.)

Table I Decoiorlzation of Pa. chlorex Decolorization of Pa. shortDecnlmiution of Pa. chlon'x refined long residuum residuum rel. shortresiduum My process, decol. xg f g z My proceflss, deco]. g fi gfi Myprofi, deco]. xg g decol. efl. decol. efl. m. an

Percent Percent Percent Fresh burned. 100 100 100 94 92 (Ap arently(Apparentg (Apparently usa le indeflusable ind usable indefinitely)nitely.) mtely.) i Aver. efl AEprox. 100 or App. 100 for 18 75% for 5 A100 for 13 69% for 4 lgher [or 18 urns. bums burns.

Decolorization of coastal acid refined Deeoloriaation of Mid-ContientDuo distillate 801 refined short rea'dnm'n Multiple Multiple My process,deool. efl. hearth My proces, deco]. ell. hearth kiln,

decol. ell. ikmL elf.

Percent Percent Percent Perm! Fresh burned 100 100 mo [m L 104 88 I07 8999 so RB 84 99 73 11B 73 97 70 107 m 94 63 101 62 105 62 107 M 60 107 Q56 99 54 57 94 53 M 103 102 50 (Apparently usable in- (Discarded)(Appupntly umble in- (Dmnled) definitely definitely) Average eiiiciencyfor 10 burns 100. 1 64.9 Approx. 100 (ii. l (35 surface of my kiln isabout 50 times that of the multiple hearth kiln which explains thetremendous capacity or my kiln with respect to its size.

Certain items of interest may ,be noted. The maximum pressure drop forair in designs having about 50% of the volume occupied by clay is about3 inches of water per foot of chamber when operating near atmosphericpressure. The amount of air used is about 10% or more in excess of thattheoretically required. At burning Thus it will be seen from the abovetable that a revolutionary improvement is obtained by the use of mymethod, 1. e., the efllciency of the clay regenerated by my method issubstantially hi her than clay which has been regenerated the samenumber of times in conventional kilns, in fact, clay regenerated by mycommercial scale process has lost hardly any of its original efliciencyeven after 18 burns while the other clay is ready to bethrownawayafter5burns. Thusitwillbe No. clays is around 70% on the same basis.on

the other hand starting with fresh clay and conducting regenerations bymy method, the'efflciency of clay after even 18 regenerations is stillaround 95-100% and the average efiiciency of No. 1 to No. 18 clays isapproximately 100%. Since a value was not obtained for every burn, theexact average efileiency is not available, however, it can be seen thatthe average would be around 100% or even higher in some cases. Thetremendously decreased clay cost" which results by use of my process isobvious from the above. Thus it would appear that the clays may beemciently regenerated forever by my process. There is a purelymechanical loss of clay, however, from handling in apparatus now usedwhich amounts to about 2% per burn so that after about 50 burns all ofthe original clay would be lost in this manner. It is to be furthernoted that the prior art operates at an average eflicieney of around 70%while I operate at an average efllciency of around 100%. Therefore, inthe filtering step alone, I obtain around increased eiilciency for theyear's operation. It will also be that of present multiple hearthburners.

noted that in some instances the efliciency of my regenerated clay isabove 100%. The probable reason for this is because the particular freshburned clay was not initially prepared most efficiently and whencarefully regenerated with proper control throughout, as provided by myprocess, the regenerated clay is more efllcient than when freshlyprepared.

In addition to the important advantage of positive temperature controlwhereby clay is reactivated to higher emciency than that obtained by theprior art, as set forth above, the present method has several otherdistinct advantages over the commonly used methods. Not the least ofthese advantages is the fact higher throughput of clay per unit volumeof burner is possible. I have varied the rate of clay throughput in myapparatus from 16 lbs./hr./cu. ft. of kiln volume to '75 lbs./hr./cu.ft. of kiln volume without any marked effect on the degree ofreactivation. In certain cases the throughput is 15 to 30 times Quiteobviously a distinct improvement is afforded by this increasedthroughput rate in substantially reducing the time required toregenerate large batches of clay. The following data clearlydemonstrates this advantage on clays of equal carbonaceous content.

Applicant's burner Multiple hearth burner Effective Effective Ulay feedrates, burning Clay rate, burning lbalcu. itJhr. surface, lbs./i cu.itJhr. surface, sq. itJcu. it. sq. ft./cu. it.

Another important feature of the present in-- vention is the efficientutilization of the heat developed in burning. More heat is developed byburning most spent clays than is required and in my process thecombustion is conducted so efliciently that no additional fuel need beadded in the usual case, in fact, in the usual case of regeneratingspent petroleum filter clays, heat is extracted by my process, beingtaken up by the liquid heat exchange medium and may be used for otherpurposes. Since the reaction is exothermic this is only as it should be,however, in every other process now in use heat must be added during theregeneration. For instance, the utilization of the heat developed byburning in the commonly used burners such as the multiple hearth typeburner is so poor due to the amount of air used, loss to surroundings,etc., that additional fuel is added to burn off the impurities, the costof this additional fuel for one average size refinery alone may be ashigh as $20,000 per year.

In the claims where I speak of solid particles or granules I mean toinclude as a part of the particles or granules any solid or liquidmatter that might be adhering to same as. for example, the solid orliquid petroleum matter adhering to spent clay.

I claim:

v1. A method of regenerating spent particles of petroleum percolationclay and similar petroleum percolation filtering material by burning edthe petroleum matter thereon with air which comprises flowing the spentparticles under regenerating conditions through a regenerating zone ofsuflicient length to afford proper treating time, flowing approximatelythe theoretical amount of air required to burn oil! said petroleummatter countercurrently through the zone in direct contact with theflowing particles so as to effect the burning of the petroleum matter,and flowing a sufllcient amount of a liquid heat exchange medium,maintained in a temperature range between the minimum combustiontemperature and the maximum combustion temperature that does not causesubstantial hea damage to the particles, within sufliciently closeindirect heat exchange to all the particles in said zone that they arenot over about 1 inches from a heat transfer surface controlled by saidliquid heat exchange medium, so that the liquid heat exchange mediumextracts heat from the particles undergoing combustion and maintainstheir temperature closely within said temperature range.

2. A method of regenerating spent particles of petroleum percolationclay and the like by burning on the petroleum matter thereon with airwithin a closely controlled combustion temperature range which comprisesgravitating the spent particles as a substantially solid column ofparticles under combustion conditions through a regenerating zone ofsuflicient length to afiord proper regenerating time, flowing airupwardly through the zone in direct contact with the gravitatingparticles by way of substantially continuous paths formed thereforthrough the particles so that the air does not force its way through theflowing particles in any substantial portion of the zone, the amount ofair used being limited -to approximately the theoretical amount requiredfor burning off said petroleum matter, and extracting heat from theparticles being regenerated in order to control their temperature byflowing a sufficient amount of liquid heat exchange medium, maintainedaround 900 F., within sufllciently close indirect heat exchange to allthe particles in said zone that they are not over about 1 inches from aheat transfer surface controlled by said liquid heat exunder combustionconditions through a com-- bustion zone of suflicient length to affordproper regenerating time, flowing the combustion-supporting gas upwardlythrough the zone in direct contact with the gravitating particles by wayof paths formed therefor so that the gas does not force its way throughany substantial region of particles, and flowing a sufficient amount ofliquid heat exchange medium, maintained within a combustion temperaturerange between the minimum combustion temperature and the maximumcombustion temperature that does not cause substantial heat damage tothe particles, within sufllciently close indirect heat exchange to allthe particles in said zone that they are not over about 1% inches from aheat transfer surface controlled by said liquid heat exchange mediumwhereby the temperature of said particles is maintained closely withinsaid combustion temperature range.

4. A method of increasing the activity of adsorbent particles of contactmaterial such as clay and the like carrying carbonaceous matter bycarbonizing the carbonaceous matter on the particles by reaction with agaseous agent within a closely controlled, elevated carbonizingtemperature range that is between the minimum carbonizing temperatureand the maximum carbonizing temperature that does not cause substantialheat damage to the particles, which comprises gravitating the particlesas a substantial solid column of particles under carbonizing conditionsthrough a carbonizing zone of suflioient length to afford propercarbonizing time, flowing a gaseous agent of restricted oxygen content,which is capable of carbonizing said carbonaceous matter, upwardlythrough the zone in contact with the particles so as to form an activecarbon layer on said particles by carbonizing at least a portion 01'said carbonaceous matter thereon, bailling the gravitating particles insuch manner as to form paths for the gaseous agent so that it passesthrough the zone in' direct contact with the particles but withoutforcing its way through any substantial region of unbaflled particles,and flowing a suflicient amount of liquid heat exchange medium, maintained within approximately said carbonizing temperature range, withinsuiliciently close indirect heat exchange to all particles in said zonethat the temperature of said particles is maintained closely within saidtemperature range.

'5. A method of treating adsorbent particles of contact material such asclay and the like with a gaseous agent within a given elevated treatingtemperature range that is closely controlled which gaseous agentupwardly through the zone in direct contact with the particles, baiilingthe gravitating particles in such manner as to form paths for thegaseous agent so that it passes through the zone in direct contact withthe particles but without forcing its way through any substantial regionof unbaflied particles, and flowing a sumcient amount of liquid heatexchange medium, maintained within approximately said temperature range,within sufliciently close indirect heat exchange to all the particles insaid zone that the temperature oi. said particles is maintained closelywithin said temperature range.

6. A method of treating solid particles with a gaseous agent within agiven elevated treating temperature range that is closely controlledwhich comprises flowing the particles under treating conditions througha treating zone of sufllcient length to afl'ord proper treating time,flowing the gaseous agent countercurrently through the zone in directcontact with the flowing particles by way of paths formed therefor sothat the gaseous agent does not force its way through any substantialdepth of particles, and flowing a suflicient amount of a liquid heatexchange medium, maintained within approximately said temperature range,within sufliciently close indirect heat exchange to all the particles insaid zone that they are not over about two inches from a heat transfersurface controlled by said liquid heat exchange medium whereby thetemperature of said particles is maintained closely within saidtemperature range.

7. A method of reacting solid particles with a gaseous agent within agiven elevated reacting temperature range that is closely controlledwhich comprises gravitating the particles as a substantially solidcolumn of particles under reacting conditions through a reacting zone ofsufficient length to afford proper reacting time, flowing the gaseousagent upwardly through the zone in direct contact with the particles toeffect said reaction, baflling the gravitating particles in such manneras to form paths for the gaseous agent so that it passes through thezone in direct contact with the particles but without forcing its waythrough any substantial region of unbaflied particles, and flowing asuflicient amount of a liquid heat exchange medium, maintained withinapproximately said temperature range, within sufli ciently closeindirect heat exchange to all the particles in said zone that thetemperature of said particles is maintained closely within saidtemperature range.

8. A method of regenerating spent adsorbent particles of a clay-typecontact material contaminated with carbonaceous impurities by burningoif the impurities with air which comprises flowing the spent particlesas a substantially solid column of particles under combustion conditionsdownwardly through a regenerating zone of suflicient length to aifordproper regenerating time, flowing the air countercurrently through thezone in direct contact with the particles so as to burn oi thecarbonaceous matter thereon, bafliing the flowing particles in suchmanner as to form sub stantially continuous, particle-free paths for theair through the downwardly flowing particles so that the air passesthrough the zone in direct contact with particles but without forcingits way through any substantial region of unbaiiied particles, andiiowing a sumcient amount oi. a liquid heat exchange medium, maintainedwithin a combustion temperature range between the minimum combustiontemperature and the maximum combustion temperature that does not causesubstantial heat damage to the particles, within sufficiently closeindirect heat exchange to all the particles in said zone that thetemperature of said particles is maintained closely within saidcombustion temperature range.

9. A method or treating solid particles in the presence of a gaseousagent within a given elevated treating temperature range that is closelycontrolled which comprises gravitating particles under treatingconditions through a substantially vertical treating zone of suflicientlength to afiord proper treating time, flowing the gaseous agentupwardly through the zone in direct contactwith the particles, bailiingthe gravitating particles in such manner as to form substantiallycontinuous, particle-free paths for the gaseous agent through theflowing particles so that the gaseous agent flows through the zone indirect contact with the particles but without forcing its way throughany substantial region of unbaflied particles, and flow-- ing asuflicient amount of a liquid heat exchange medium, maintained withinapproximately said temperature range, within sufllciently close indirectheat exchange to all the particles in said zone that the temperature ofsaid particles is maintained closely within said temperature range.

' JOHN W. PAYNE.

